Endodontic reamer and a method for manufacturing endodontic reamers and files

ABSTRACT

An endodontic reamer and a method for manufacturing endodontic reamers and files, more specifically an endodontic reamer having a cylindrical shaft and a working portion extending forward from a removed end of the shaft. The working portion includes, typically, a pair of wedged shaped projecting sections that extend beyond the diameter of the shaft. Forward from the wedge shaped sections is a nose, typically non-cutting nose, that has a diameter of about equal to diameter of the shaft. There are typically two (2) wedge shaped sections projecting outward opposite one another. Applicant also provides a novel method for manufacturing an endodontic reamer, which consists of using a two piece mold and placing a wire blank between the mold, followed by forcing the mold together, under compression, against the wire blank, to deform the blank into the shape of the mold parts.

[0001] This application is based on and claims priority from provisionalpatent application, Serial No. 60/294,527, filed May 30, 2001.

FIELD OF THE INVENTION

[0002] An endodontic reamer and method for manufacturing endodonticreamers and files, more specifically a novel endodontic reamer compriseda longitudinal shaft having projecting wedges, and a novel method offorming an endodontic instrument with compression.

BACKGROUND OF THE INVENTION

[0003] The field of endodontics involves diseases of the tooth pulp,commonly known as a root canal, and typically requires the dentist toremove infected material from within the pulp of the tooth. The rootcanal itself is the space within the tooth that carries the blood supplyinto the tooth and contains the pulp. Within the root canal the pulpcontains the nerve endings, which causes pain to warn when one bitesdown too hard on a hard object. From time to time, this space (the rootcanal) becomes infected and requires the dentist to clean (ream) out theroot canal space in order to remove the pulp and/or other infectedmaterial. This cleaning consists of using a series of instruments toremove the pulp and infected material by enlarging and conically shapingthe canal. Once cleaned and shaped, the space is sealed so that it doesnot become reinfected once again. It is the dentist's goal to providecomplete cleaning by removing as much of the infected material aspossible. The more infected material that is removed, the more likelythe case has of being successful and thus the tooth saved. Otherwise,the tooth must be extracted and the space filled with a false tooth ortreated by other means.

[0004] Endodontic reamers typically have helically wound cutting edges(blades). Rotation of the reamer allows the cutting blades to workwithin the root canal to cut dentin and remove infected material fromthe walls of the canal. Applicant has invented a novel endodontic reamerfor effective cutting and removing of material that overcomes manylimitations of the prior art of helically wound reamers. Applicant'snovel endodontic reamer is comprised of a shaft having a longitudinalaxis and wedge sections, not helically wound, with respect to thelongitudinal axis.

[0005] Applicant provides a novel reamer for engagement at first endwith a handle for manual manipulation or powered by a dental handpieceand a second end for engagement within the root canal of a patientrequiring root canal therapy. Typically, the wedges are wider than thediameter of the shaft. Furthermore, the shaft is typically flexible asopposed to being rigid. This flexibility helps allow the reamer to staycentered within the root canal. The Applicant's wedges include forwardand trailing portions that are typically at an angle oblique to thelongitudinal axis. One or more cutting edges, which in a preferredembodiment may be straight, are typically provided - radiating outwardaround the shaft. A novel pilot tip guides the flexible shaft within thecanal. The pilot tip can be cutting or noncutting.

[0006] The novel endodontic reamer's cutting blades can be typicallyvery narrow and sharp; increasing it's cutting efficiency and reducingthe number of instruments required by the dentist for treatment.Reducing the number of instruments also reduces the treatment time forboth the dentist and patient. The cutting blades are typically made verythin, thus reducing the surface area contact of the blade with the rootcanal walls. These thin blades (typically from 0.01 mm to 1.00 mm thickpreferably from 0.05 mm to 0.25 mm thick) also allow for more space forthe previously cut material to reside before being irrigated andsuctioned from the canal. When compared to prior art, this extra spacehelps reduce the loss of cutting efficiency that the cut material oftencauses by interfering with the cutting action of the blades. Thin bladesincrease cutting efficiency and reduce torsional stress on the shaft.Stress by torsion (twisting along the long axis of the shaft) is aprimary cause of premature instrument breakage.

[0007] Applicant's reamer is manufactured by a novel method. This methodincludes using wire of the same diameter as the shaft of the finishedproduct. The wire form may be cylindrical or tapered and be made fromnonmetal or metals such as nitinol, stainless steel, and carbide steel.The wire provides the “blank” for the reamer. A second end of the wire,near the cutting portion is located and then swaged, coined, hot or coldformed, forged, pressed or otherwise subjected to mechanical compressionto “flare” the second end such that it is flattened - thereby, having awidth greater than the unflattened (round portion) of the wire andhaving a thickness narrower then the rounds portion in the otherdimension. The leading edge of the flattened portion may be polished,machined, sheared or further formed into a sharp cutting edge.

[0008] In prior art, endodontic reamers have been ground into thedesired shape. This grinding process is time consuming, requires manyprocedural steps and requires the use of very specialized, expensivemachinery. This grinding process also generates imperfections andflawing on the surface of the finished work piece. These imperfectionsand flaws on the reamer's surface may lead to premature failure,increasing the risk to the patient, reducing the reamer's useful lifeand causing it to be more expensive for the dentist to use. This cost isthus passed onto the patient in the form of higher treatment costs. Thusfor economic, rather than biological reasons, teeth are beingunnecessarily extracted rather than saved.

[0009] Applicant's also provide for a novel process of manufacturing adental instrument, including the novel reamer. Because the novel shaftis made without grinding the outside surface down to the desired thediameter, typical of prior art, less material is removed (wasted) andless material must be handled for disposal. Of significant importance,the surface of the shaft is not marred through the grinding process. Theinstrument's fatigue life is extended because the surface of the shaftis kept in its original state as when drawn into wire form. Finally,this simplified forming process allows for less complex and lessexpensive equipment to be used for manufacturing. The time tomanufacture such an instrument is reduced. Less specialized equipmentand the elimination of the time required to grind down the shaft reducesthe cost of manufacturing such reamer.

[0010] Applicants also provide a novel handle, the handle for holding afile or reamer. Applicants' novel handle may include a shank. The shankis cylindrical and is designed to engage a file or a reamer. Applicants'novel handle includes a portion, typically along the shank, having areduced diameter. This reduced diameter may take the shape of a groove(U-shaped) or a notch (V-shaped). By providing such a reduced diameter,Applicants provide a predictable break point, such that a file or reamerdoes not break in the tooth, but at the break point at the reduceddiameter. In other words, rather than having a file or reamer breakalong a shaft or other part thereof, and thus be difficult to retrieve,Applicants' novel handle with a reduced diameter will break first and,will be far easier to retrieve from the tooth than a piece of a file orreamer that may be deep within the canal of the tooth.

OBJECTS OF THE INVENTION

[0011] It is the first object of Applicants' invention to provide anovel spade type drill, the spade drill having a working portion with aplurality of flutes or wedge shaped portions extending beyond thediameter of the shaft to define working portions, the working portionswhich cut the tooth.

[0012] It is a second object of Applicants' present invention to providefor a novel method of manufacturing a spade type reamer. The novelmethod includes compressing a cylindrical elonged wire blank or sectionbetween a pair of molds under compression to force the material todeform and take the shape of the molds.

[0013] It is a third object of Applicants' present invention to providea novel handle, the handle for holding a file or a reamer, the handleincluding a portion which is grooved or notched to provide for aweakness or weak point at which the shaft may, under rotation, break ifthe cork on the shaft exceeds a predetermined value.

A BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 illustrates a side elevational view of a preferredembodiment of Applicants' present invention (left side and right sideviews being identical), this view representing the view in FIG. 1rotated 90 degrees.

[0015]FIG. 2 illustrates a top view of a preferred embodiment ofApplicants' present invention (top and bottom views being identical), asillustrated in FIGS. 1 and 2.

[0016]FIG. 3 presents an end elevational view of an alternate preferredembodiment of Applicants' present invention (looking towards the nose),as illustrated in FIGS. 1 and 2.

[0017]FIG. 1A illustrates a side elevational view of an alternatepreferred embodiment of Applicants' present invention (left side andright side views being identical).

[0018]FIG. 2A illustrates a top view of an alternate preferredembodiment of Applicants' present invention (top and bottom views beingidentical), this view representing the view in FIG. 1 rotated 90degrees.

[0019]FIG. 3A presents an end elevational view of the alternatepreferred embodiment of Applicants' present invention (looking towardsthe nose), as illustrated in FIGS. 1A and 2A.

[0020]FIG. 4 is a perspective view of the preferred embodiment ofApplicants present invention that is illustrated in FIGS. 1, 2 and 3.

[0021]FIG. 5A represents a side elevational view of an alternatepreferred embodiment of Applicants' present invention, having fourfluted or wedge shaped projections radiating outward from the axis ofthe shaft.

[0022]FIG. 5B is an end view, looking into the nose, of the alternatepreferred embodiment of Applicant's present invention that isillustrated in FIG. 5A.

[0023]FIG. 6 is a side view and FIG. 7 a top view of a novel method ofmanufacturing a dental instrument such as a file or reamer bycompressive forces applied to a mold.

[0024]FIGS. 8 and 9 represent side and bottom views respectfully of twopairs of molds for manufacturing Applicants' novel reamer comprising apair of opposed wedge shaped or fluted working portion, FIGS. 8A and 9A,and FIGS. 8B and 9B representing a preferred embodiment of mold pairsfor manufacturing Applicants' novel reamers.

[0025]FIGS. 10 and 11 illustrate two alternate preferred embodiments ofApplicants' handle, Applicants handle including means to break orseparate at a predetermined torque.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026]FIGS. 1, 2 and 3, 1A, 2A and 3A represent alternate preferredembodiments of Applicant's novel reamer (10).

[0027] The referenced figures illustrate anovel reamer (10) comprised ofa shaft portion (12) the shaft portion (12) having radius R and diameterD and a longitudinal axis La. Extending forward from the shaft portionof the reamer is a working portion (16). The working portion of thereamer typically includes that portion of the reamer that is activelyinvolved in the cutting of the dentin.

[0028] The reamer has a first end (14 a) and a second end (14 b), thesecond end being adapted for the receipt of a handle (not shown) or forreceipt into a motorized drive tool that will inpart a circular motionto the reamer. It is noted with reference to FIGS. 1 through 3 and 1 Athrough 3A that the shaft ends and the working portion begins where thereamer begins to become narrower in a first view (See FIGS. 1 and 1 A)and wider in a second view (See FIGS. 2 and 2A). This point is thebeginning of the working portion, which working portion extends throughto the first end of the reamer. With particular reference to FIGS. 1 and2 and 1 A and 2A note that both embodiments illustrate a projectingsection of the working portion, the projecting section being thatsection which extends beyond radius R of the shaft as measuredperpendicular to the longitudinal axis. Further note that the shaft hasa longitudinal axis La that is coincident with a longitudinal axis ofthe working portion. The embodiment set forth in the above referencedfigures illustrates a reamer with a pair of oppositely locatedprojecting sections. However, reference to FIG. 5 illustrates that theremay in fact be more projecting sections, each with a working portionextending beyond the radius of the shaft.

[0029] Reference to the accompanying figures also illustrate that theshaft is substantially longer then the working portion and is flexible,providing for a working portion that may bend as it encounters a changein direction in the channel of the tooth. Typical lengths of shaft rangefrom 1.0 mm to 100 mm (preferred 10 mm to 50 mm) and typical workingportions range from 0.25 mm to 10 mm (preferred 1.5 mm to 3.0 mm), butthe working portion is typically substantially shorter in length ascompared to the length of the shaft (typically 3% to 25%) This allowsfor the requisite flexibility of the shaft.

[0030] The working portion may be seen to include a pair of opposedwedges (18) where in a first view (FIGS. 2 and 2A) the width firstwidens then reaches an apex (20), then narrows until it reaches thediameter of the shaft. The wedges (18) are seen, in a second view (FIGS.1 and 1A) to first become thinner until they reach a minimum at apex(20) then thicker until they reach a thickness equal to the diameter ofthe shaft).

[0031] The working portion starts at the removed end of the shaft. Theprojecting sections or wedges 18 define an apex. Forward of the apex isa leading portion which extends forward of the apex and makes an angleof less than 90° with the longitudinal axis of the reamer. This is bestseen in FIGS. 2 and 2A. The leading edge portion of the embodimentillustrated in FIGS. 1A, 2A and 3A has a rectangular outline. The shaftdiameter may be between 0.01 mm and 3.00 mm and the length between 1.0mm and 100.0 mm. The thickness at the apex may be between 0.009 mm and2.99 mm.

[0032] Turning again to FIGS. 1, 2 and 3 and 1A, 2A and 3A it is seenthat in views 2, 3, 2A, 3A the projecting portion reaches a maximumdimension at a widest point, apex 20 and, when viewed in FIGS. 1 and 1Aa thinnest point or portion. Forward of the apex, Applicant's novelreamer includes a leading portion (22), the leading portion extendingfrom the apex to nose 24 a, (FIGS. 1 through 3) or nose 24 b, (FIGS. 1Athrough 3A). The nose portion is equal to or less than the diameter ofshaft (12) as measured in the longest dimensioned taken perpendicular tothe longitudinal axis of the reamer. As mentioned above the longitudinalaxis of the shaft and longitudinal axis of the working portion arecoincident.

[0033] Applicant's embodiment illustrated in FIGS. 1 through 3 describesanose (24 a) that is circular in cross-section, the cross-section beingtaken perpendicular to the longitudinal axis, and a tip (26 a) that ishemispherical. The embodiment illustrated in FIGS. 1A through 3Adiscloses a nose (24 b) that is rectangular in cross-section, whereinthe cross-sections taken perpendicular to the longitudinal axis of thereamer. Tip (26 b) of nose (24 b) is best described as hemicylindrical.

[0034] Turning back to the embodiment illustrated in FIGS. 1 through 3it is noted that the leading portion (22) is shown to have a pair ofprimary cutting portions (28 a) and (28B) when viewed in FIG. 3. FIG. 3is the view that the canal of the tooth “sees” as the instrument worksits way downward into the tooth. The arrow indicates the direction ofrotation. If the direction of rotation were reverse portions (28 a) and(28 b) would shift to the opposite opposed corners. Compare the primarycutting portions (28 a) and (28 b) of the embodiment illustrated inFIGS. 1 through 3 with the primary cutting portions (30 a) and (30 b) inFIGS. 1A through 3A.

[0035] A section taken perpendicular to the longitudinal axis in theembodiment illustrated in FIGS. 1 through 3 on the leading portion wouldreveal edges where the same view taken in the embodiment illustrated inFIGS. 1A through 3A would illustrate a rectangle. Both instrumentsprovide for effective cutting but testing is shown that when therectangular nose embodiment encounters a channel narrower than thediameter of the shaft the nose portion may begin to cut aggressively.With the nose portion illustrated in FIGS. 1 through 3 (a circular nose)the nose does not having a cutting edge.

[0036]FIG. 4 is a perspective view of the embodiment of Applicantsreamer that is illustrated in FIGS. 1, 2 and 3.

[0037] Please see FIGS. 6 and 7 for the novel method by which Applicant,manufacturers this or any other type of endodontic reamer or file. Manytypes of drills have been formed by methods such as those found in U.S.Pat. No. 5,816,807, the specifications of which are incorporated hereinby reference. These patents disclose the manufacture of dental drills byremoving or grinding material from the work piece. They do not discloseApplicant's novel method of swaging, stamping, coining, pressing forgingor forming as set forth in FIGS. 6 and 7. FIGS. 6 and 7 illustrate atwo-piece die or mold, M, and a force of other source of compression, F.The wire material or blank WB (which may be cut to length, asillustrated, or inserted between two pieces of the mold as unrolled froma spool), is placed between the two pieces of the mold. Compressionforce is applied as illustrated and deformation on the wire blank forcesit into the shape of the finished piece. The process may require one ormore “hits” from one or more directions to achieve the desired result.The blank may be constructed from the following materials: nitinol,stainless steel, carbide steel or other steel, plastic, graphite,composites or any other suitable material. The blank can be of any crosssectional shape and have a parallel or tapered shape before forming.Some typical mold shapes are illustrated in FIGS. 8A and B, and 9A andB. Before forming, the dimensions of the blank may be as follows: 0.01mm to 3 mm in diameter (preferred 0.10 mm to 1.00 mm) and 1 mm to 100 mm(preferred 10 mm to 60 mm) in length, or any other suitable dimension.

[0038] The novel method of manufacture allows dental endodontic reamersand files to be made more efficiently and economically. Prior artrequires time-consuming processes with many manufacturing steps.Material is wasted which then must be disposed of properly. The surfaceof the blank is often marred during manufacturing, therefore the usefullife is shortened making the instrument more costly for the dentist.Patients are losing their teeth to extraction rather than being savedbecause of the high cost of producing these instruments.

[0039] The novel manufacturing process requires compressive force andtool dies to form the desired shape. The process can form many pieces ina very short period of time. The machines required to form the parts arepresses, four slide or multi-slides, or any custom press. These machinesare commonly used in making many different parts for many differentindustries (but are not typically used in the dental industry to makereamers) and therefore they are relatively inexpensive to acquire, setup and maintain. With this new method of manufacturing, it isanticipated the cost of making a dental instrument such as a reamer willbe one-fifth of the current cost to manufacture.

[0040] Please see FIGS. 10 and 11 for two preferred embodiments of anovel handle (25, 26) for this or any other type of endodontic reamer.The handle usually includes a body (34) at a proximal end and a shank(32) at a distal end, the shank cylindrical with a smaller diameter thanthe cylindrical body (34). The shank receives the reamer or file. Thehandle itself can be configured in many different shapes. Prior artdescribes reamers and files with handles attached for manual operation,or handles designed to fit into a dental handpiece for mechanicalpowered operation. Applicant's novel handles (25, 26) describe a groove(25A) (“V” shaped) or notch (26A) (“U” shaped) manufactured into thehandle, typically along the shank (34). This notch (25A) or groove (26A)may be of various configurations, however; it serves as a predictable“breakpoint” when excessive torque is applied to the reamer or file whenin use. The notch or groove defines walls having a diameter reduced fromthe walls immediately adjacent thereto on either side thereof; the notchor groove in the outer surface of the shank or body of the handle. Priorart, without this novel handle, may break unpredictably at the weakestpoint on the instrument. Unfortunately, this unpredictable break pointoften occurs deep inside the tooth making it virtually impossible forthe dentist to retrieve the broken fragment. By knowing the minimumtorsional load the instrument is able to withstand before breaking, andthrough careful engineering calculations based on the material of thehandle, the depth of the notch or groove can be cut so that the handleitself will break before the reamer or file breaks. Breaking at thispredictable point allows the instrument to be retrieved from the canalbecause it gives the doctor a “handle” to grasp and pull the brokenfragment out of the root canal and because it breaks at a point easily,accessible instead of inside the canal.

[0041] The groove or notch will typically have a reduced diameter in therange of 25% to 75% of the diameter of the shank. For example, if theshank diameter is 0.90 mm, the depth of the groove or notch will be inthe range of 0.23 mm to 0.68 mm.

[0042] While particular embodiments of the present invention have beenshown and described, it will be obvious to those skilled in the art thatchanges and modifications may be made without departing from theinvention in its broader aspects. Therefore, the aim in the appendedclaims is to cover all such changes and modifications as fall within thetrue spirit and scope of the inventions. The matter set forth in theforegoing description and accompanying drawings is offered by way ofillustration only and not as a limitation. The actual scope of theinvention is intended to be defined in the following claims when viewedin their proper perspective based on the prior art.

I claim:
 1. A process for manufacturing a dental instrument having aworking portion, the process comprising the steps of: providing a wireand a die, the die having walls defining, at least in part, the shape ofa working portion of the dental instrument; placing the wire adjacentthe die; applying a compressive force to the wire, sufficient to deformthe wire into a shape reflecting the walls of the die defining theworking portion of the dental instrument; and, releasing the deformedwire from the die.
 2. The process of claim 1 wherein the providing stepincludes providing a wire constructed of: Stainless steel, carbidesteel, or other steel, nitinol, plastic, composite, graphite, or anyother suitable material.
 3. The process of claim 1 further including afinishing step, wherein the finishing step includes the removal ofmaterial from the deformed wire.
 4. The process of claim 3 wherein thefinishing step includes the step of polishing at least some of theworking portion of the deformed wire.
 5. The process of claim 1 whereinthe applying step is repeated more than once.
 6. The process of claim 5wherein the wire blank is repositioned with respect to the die betweenat least a pair of respective applying steps.
 7. The process of claim 1wherein the wire of the providing step has a diameter between 0.01 mmand 3.00 mm and the deformed wire has a length of between 1.0 mm and 100mm.
 8. The process of claim 1 wherein the die consists of two or moresections and the wire is placed between the sections before the applyingstep.
 9. A dental instrument having: an elongated flexible cylindricalshaft, the shaft having a longitudinal axis and a radius R, the shafthaving a near end and removed end; and a working portion, extendingbeyond removed end of the shaft and including a longitudinal axiscoincident with the longitudinal axis of the elongated shaft, theworking portion including at least one projecting section, eachprojecting section extending beyond a radius R and defining an apex, theprojecting section including a leading portion extending forward of theapex and making an angle with the longitudinal axis of less than 90° anda trailing edge portion, the trailing edge portion extending rearward ofthe apex and making an angle of less than 90° with longitudinal axis,the projecting section having thickness T at the apex.
 10. The dentalinstrument of claim 9 wherein shaft portion has a diameter of between0.01 mm and 3.00 mm and a length between 1.0 mm and 100.0 mm.
 11. Thedental instruments of claim 9 wherein the working section has athickness of between 0.009 mm and 2.99 mm.
 12. The dental instrument ofclaim 9 wherein the leading edge portion has a rectangular shape. 13.The dental instrument of claim 9 wherein the leading edge portion is atleast partially convex in cross-section.
 14. The dental instrument ofclaim 9 wherein the at least two projecting sections includes a pair ofdiametrically opposed projecting sections.
 15. The dental instrument ofclaim 14 wherein the leading edge portion has a rectangular shape. 16.The dental instrument of claim 14 wherein the leading edge portion is atleast partially convex in cross section.
 17. The dental instrument ofclaim 14 where the projecting sections have a thickness between 0.009 mmand 2.99 mm.
 18. The dental instrument of claim 14 comprised of one ofthe following: stainless steel, nitinol, plastic, composite graphite andcarbide steel.
 19. The dental instrument of claim 14 wherein the shaftportion has a diameter of between 0.009 mm and 3.00 mm and length ofbetween 1.0 mm and 100.0 mm.
 20. A dental instrument, the dentalinstrument comprising: a cylindrical shank, the shank with wallsdimensioned, for engagement with a file or reamer, the cylindrical shankhaving an outer surface, the outer surface with walls having a reduceddiameter compared to walls adjacent thereto.
 21. The dental instrumentof claim 20 wherein the walls having a reduced diameter define a notch.22. The dental instrument of claim 20 wherein the walls having a reduceddiameter define a groove.
 23. A dental instrument comprising: acylindrical shaft having a longitudinal axis and a diameter; a workingportion with a longitudinal axis of the shaft, the working portionincluding a pair of opposed wedge shaped sections and a nose, the noseforward of the pair of wedge shaped sections.